1. Technical Field
The invention relates in general to a receiver and a signal receiving method thereof.
2. Background
The orthogonal frequency division multiplexing (OFDM) modulation technology can be used in wireless communication systems and digital audio and video broadcasting systems to perform high spectral efficiency transmission. Based on the OFDM modulation technology for the multi-carrier modulation, the effective processing ability is obtained with respect to the multi-path reflection effect. Therefore, a receiver in the OFDM system only needs one simple one-tap. So, the OFDM system has recently become the mainstream technology in the communication field and the broadcasting application development. Various systems, such as the digital audio broadcasting (DVB), the high definition TV (HDTV) and the wireless local area network (WLAN) IEEE 802.11a/g, use the OFDM transmission technology.
In the wireless communication system, a transmitter transmits wireless signals to a receiver through a physical channel, such as air, in the form of electromagnetic waves. Due to the non-ideal channel effect, such as multi-path reflection and multi-path fading, the wireless signals received by the receiver may get distorted. Inter-symbol interference (ISI) caused by the multi-path channel can be easily cancelled by adding a guard interval (GI) with longer duration than duration of a channel impulse response to the symbols. However, if the multi-path signal received by the receiver has a larger delay spread, the duration of the channel impulse response will be longer than the duration of the GI, thus a residual ISI effect is caused and the system performance is reduced.
In addition, an inter-carrier interference (ICI) effect is caused when the orthogonality of the sub-carriers is destroyed, and the system performance is reduced likewise. Therefore, it is an important issue in the field to solve the reduced system performance problem caused by the residual ISI and ICI without increasing the system computation complexity.